Hidden connectors?

[Xenon]

Hi,

Intro: One of my ABS-sensors (RL) is acting crazy, because in Evoscan it reports a wheel speed of 184km/h while the VR4 is parked!
If I start driving the car, the readout of this RL-sensor decreases, while all other wheelsensors -as expected- report an increasing speed. I assume this will cause my AYC-light to come on when I start driving. However, AYC's DTC reports 82 (pump fail).

My guess is that the sensor's cable might be damaged, or the connector might not be fitted well, got dirty, corroded. Whatever.

To find out, I need to locate the RL sensor connector. Both rear sensor wires go through two oval shaped holes at the top of the rear subframe and... seem to disappear at that point? Does anyone know where these wires (and finally connectors on it) go?

Many thanks in advance!

[Nick Mann]

They connect on the top of the rear subframe. If you put your hand up and over the subframe (eg from the front edge of the back box) you can just get your fingers to the connectors.

[Xenon]

Great! Thnx! Gonna try it again today

Is the connector fixed on top of the subframe, or is it possible to pull it down a little to get a visual on it?

[carlos-1975]

its held in with them silly clips. you can reach it and find the bit needed to press down to split it though

[Nick Mann]

The loom side is fixed up there somehow - I have never looked at one from the right angle to tell you how. The sensor end has a tab on the top that can be depressed which allows the plug to slide out and down through the hole.

It's a fiddly job because of the lack of space and the fact you can't see the plug/socket, but it is doable.

I'm not sure where the wires go on the loom side, so can't suggest a place to check it out further upstream.

[Xenon]

This info should be of enough help to me.
Many thanks!

[Xenon]

Jeeee, there is absolutely no way I can get up there
Apparently my wrists are not that flexible as they should be...

But I need you guys help me to sort out the following facts, gathered with Evoscan:

1. Started with clearing all present DTC's in EFI, ABS and AYC
2. Operated all actuator options manually in ABS-mode
3. Operated all actuator options manually in AYC-mode
4. ABS DTC's are confusing, because it complains about all wheelsensors -> both front sensors open + all sensors shorted (???) + some unidentified trouble codes
5. AYC DTC's -> None
6. Monitoring ABS while parked results in all wheel speeds @ 145km/h
7. Monitoring AYC while parked results in a RL wheel speed of 184km/h, all others report 0km/h (which makes sense, even to me )
8. Decided to do a slow drive while logging ABS resp AYC
9. Slow drive: the RL wheel decreases heavily from 184km/h to approx 135km/h while doing only a 10km/h drive. All other wheels increase, fairly the same amount and matching the "Vehicle Speed" readout of approx 10km/h (see attachment)
10. As soon I start driving away, I can hear the AYC-pump starting up in the back. It runs for aprox 8 to 10 seconds, then stops with an upcoming AYC-light and DTC "Pump Fail 1"

This is fairly about what's going on. My guess is that it would be a good start to replace the RL ABS-sensor, because it's likely that this little fellow screws up the picture of what's really going on underneath.

On the other hand, I don't understand how sensors can be marked as open and shorted at the same time, while reporting a realistic value (exept for RL) while logging?

Anyone ideas? Please shoot!

[Nick Mann]

I'm not sure evoscan AYC troubleshooting is a good bible for the VR4. The evo and the VR4 do not do exactly the same thing so some of the info might be misleading.

The AYC issue sounds like either a tired pump or a dodgy pressure switch. An adjustable pressure switch can potentially solve either problem.

I'd also go for a speed sensor change on your RL hub, simply based on your findings above.

[Xenon]

Thnx Nick, might be a good point about AYC-compatibility issues between EVO and VR4. I will ask Limitless if they can confirm this.

Right now, I don't know anything yet about AYC-pump behaviour, pressure switches and so on. In fact, the inner workings of all AYC-stuff is still a mistery to me, so I have something to study on .

But am I right that even in case of a tired pump (or switch) it won't do any harm to drive with?

[Xenon]

Somebody (living nearly next to my door) offered me a spare sensor, which I already will receive by tomorrow morning. So I now have to find a way to get it in place...

[Davezj]

i would get the code from the dash board flashing and ignore what evoscan tells you with regards to error codes as i have had loads of error showing up on evoscan and no code displayed on the dash. alway go for the dash reading codes.

evoscan is great for data logging but it does not handle the error code very well at all. hopefully this will get sorted at some point by haymish at limitless. but it's a good bit of kit especially for the price of $25 USD and a £18 VAG com cable off ebay.

[Xenon]

i would get the code from the dash board flashing and ignore what evoscan tells you with regards to error codes as i have had loads of error showing up on evoscan and no code displayed on the dash. alway go for the dash reading codes.

I did. And I'll keep your comment in mind anyway.
But at least for this AYC-error, both error codes match: The AYC-light flashes code 82 while Evoscan comes up with "Pump Fail"

As far as ABS DTC readout concerns, you definitly may have a point here because the DTC results gathered don't make sense at all.

evoscan is great for data logging but it does not handle the error code very well at all. hopefully this will get sorted at some point by haymish at limitless. but it's a good bit of kit especially for the price of $25 USD and a £18 VAG com cable off ebay.

Beside the MUT, is there another recommended software tool which is sort of "CVR4 approved" if it comes to DTC readout?

[Nick Mann]

I'm not aware of any DTC reading kit for the VR4, except the MUT2.

You should have a red AYC on your dash when you start your car. That should go out. You should hear the pump - maybe not from in the cabin, but get someone to listen at the back of the car, or you listen whilst someone else starts it up. If the red light comes back on again within a few metres of driving, odds on it is your pump or switch that is the issue. I have had code 82 in the past and a new switch solved the problem.

Driving with your red ayc light on should not cause any extra harm to your system, AFAIK.

[Xenon]

Thanks again Nick. My AYC-light behaves exactly as described by you.
So now, I know what I have to look after. And that it's not a high priority fix.

I'll focus on the wheelsensor first. Thanks for all the help @ all

[Davezj]

so do you have any error code for the ABS flshed up on the dash.

if not, then there is no problem and it just evoscan giving false reading.

up to now you have only said the ayc 82 code comes up on the dash and as nick says is probably just a pressure swith.

[Xenon]

so do you have any error code for the ABS flshed up on the dash.

if not, then there is no problem and it just evoscan giving false reading.

up to now you have only said the ayc 82 code comes up on the dash and as nick says is probably just a pressure swith.

The ABS-light only flashes in diag mode, without reporting a specific code. Just flashing the same way as the EFI and N(eutral) light do in diag mode.
The TCL OFF-light however flashes (if I recall well? Not 100% sure) code 76. I have no clue of what error this code stands for. But my guess is that TCL reliability depends on correct wheelspeed data anyway and will disappear after replacing the sensor?

[Nick Mann]

According to the info in this thread:
http://www.clubvr4.com/forum/showthread.php?t=22930
the code is a difficult one to interpret! It is listed as "channel of engine ecu" or something?

If you have major wheel sensor issues then you will be getting tcl codes, ayc codes and abs codes IMO.

[Xenon]

Got another spare set of sensors today. I'm thinking of cutting the sensor wire half way, somewhere it's rather accessible, instead of neatly disconnect it on top of the rear subchassis. If the wire is carefully sealed, it would do the job as good as... new?

I'm anxious to find out if everything (AYC/ABS/TCL) is going to work as advertised and warning lights will stay off.

To be continued...

[White Lightning]

I'm thinking of cutting the sensor wire half way, somewhere it's rather accessible, instead of neatly disconnect it on top of the rear subchassis. If the wire is carefully sealed, it would do the job as good as... new?

I have heard this is a bad idea. I can't remember the specifics but it's something to do with the sensitive nature of the sensor and cutting and splicing the cable cause even more problems. I would go for the proper disconnect and replace if you can.

[Davezj]

there sensors are a very low resistance and the abs wheel passing by the hall effect sensor cause the resistance to change, it is this that is picked up by the ecu. so if you do a botch job of the connection and increase the resistance then it will effect the operation of the sensor.

be warned